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    <title>Document</title>
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<body>
    <script>
        // i在外部
        function test1() {
            var num = []
            var i
            for (i = 0; i < 3; i++) {
                num[i] = function () {
                    console.log(i)
                }
             num[i]();

            }
            return num
        }

        // i在内部
        function test2() {
            var num = []
            for (var i = 0; i < 3; i++) {
                num[i] = function () {
                    console.log(i)
                };
                num[i]();
            }
            return num
        }
        test1();
        // test2();
    </script>
</body>

</html>